I wasn't assuming anything, just using that number as an example.
We were discussing immigrants coming through Mexico, but that's not the only place where they enter the US but pointing out that the number of immigrants coming in last year is <1% of the US population shows that you're not seeing the problem- we can't house, feed and care for US citizens now, how will we do these for more? The link shows the number of immigrants coming in during 2010-2017 is far more than the 2 million coming through Mexico.
International migrant stock is the number of people born in a country other than that in which they live. It also includes refugees. The data used to estimate the international migrant stock at a particular time are obtained mainly from population censuses. The estimates are derived from the...
www.macrotrends.net
15 million is only about 4.5% of the US population.