US President Donald Trump recently cited the immigration row in Germany to defend his own controversial policies, but how similar are the two nations when it comes to migrants?
"We don't want what is happening with immigration in Europe to happen with us!" Mr Trump said.
Mrs Merkel is in the middle of a serious domestic row within her coalition government over immigration policy.
Who are the migrants and why are they coming?
An estimated 1.2 million asylum seekers entered Germany during the migrant crisis of 2015-2016, more than half from war-torn Syria, Iraq and Afghanistan.
Ongoing violence and crippling poverty are the main reasons for migrants from the Middle East to seek asylum in Europe.
Among Syrian and Iraqi asylum seekers, one phrase commonly heard on the migration route north was "Europe invited us" or "Merkel invited us".
Migrants in the US are also largely fleeing armed conflict and extreme poverty, as well as gang-related violence.
Most are from Mexico and what is known as Central America's Northern Triangle region - Honduras, Guatemala, and El Salvador.
An estimated 10% of the population in the Northern Triangle has fled to other countries due to the dangerous conditions.
What's the scale of the problem?
More than one million migrants arrived in Germany as part of Mrs Merkel's open-door policy in 2015.
The numbers have since declined: over 720,000 people applied for asylum in 2016 compared with 200,000 last year.
This decrease is largely due to an EU deal with Turkey and new border fences in the Balkans.
The number of families trying to enter the US overland without documentation is on the rise - comparing May 2018 and 2017, the rise this year was of 160%.
The Pew Research Center reported that from 2007-2015, the unauthorised immigrant population in the US from the Northern Triangle in particular grew 25%.
How are authorities dealing with it?
Germany's new interior minister, Horst Seehofer, is pressing ahead with controversial plans to hold asylum seekers in centres until their right to stay is determined.
Under Mr Seehofer's proposals, migrants are to be kept in so-called "anchor centres" for up to 18 months while their requests are processed.
Mr Seehofer also wants police to have the power to turn away undocumented migrants at the border.
Officials say the first centre is likely to be set up in Bavaria this year.
Under the Trump administration's crackdown on illegal border crossings, adults attempting to cross outside of official entry points are placed in custody and face criminal prosecution.
It is a change to a long-standing policy of charging most of those crossing for the first time with a misdemeanour offence.
Between 19 April and 31 May there were nearly 2,000 family separations.
As a result, hundreds of children are now being housed away from their parents in detention centres, including warehouses, converted supermarkets and possibly tents.
What's the political fallout?
Chancellor Angela Merkel was widely criticised over her decision to open Germany's borders during Europe's refugee crisis in 2015.
The backlash sparked by her policy helped fuel the country's far right in last year's election and led to the worst electoral performance in almost 70 years for her CDU party.
Mrs Merkel has flatly refused to back Mr Seehofer's plan to turn away migrants at the German border if they have already registered elsewhere in the EU.
Now, there is a risk that the Christian Social Union could break away from the coalition, or at least trigger a confidence vote in Mrs Merkel's leadership.
On Monday, Mr Trump called the family separations "tough and horrible" but added that the "US will not be a migrant camp".
Democrats - and numerous Republicans, including House Speaker Paul Ryan - have said the president's hardline approach is not the answer.
The United Nations has called on the US to immediately halt the separations.
Last week, House Republicans pitched draft immigration legislation that would end the separation of children and parents at the border, but it remains unlikely to pass.