The US doesn't have exclusive rights to "America" as a name. In fact strictly speaking "Gulf of America" is not a bad name since it is the largest gulf in the Americas AFAIK.

Canada has more land mass than the US does. Perhaps Trump should be talking about integrating the US into Canada (and doing away with the now-redundant US Presidential position).

But Mexico has 63 more miles of coastline on the Gulf than the USA does.

USA != America. USA is a country that resides on the North American Continent.

While I know Trump is doing this to try and claim it as the USA's... It actually makes sense if you actually use "America" properly to refer to North, Central and South America.

But Mexico has 63 more miles of coastline on the Gulf than the USA does.

He'll solve that too.