Let me see if I have got this right!

As watermelons are not available in your local area at present, they are imported from Mexico.

To get Mexico to curb immigration into the USA, President Trump has imposed economic sanctions on all Mexican products by introducing tariffs - 5% to begin with and rising to 25%.

The proceeds of these tariffs go straight to the USA Treasury and the cost is passed on to the consumer.

At some point, the consumer will find the price of watermelons too expensive and will not purchase them.

The result will put the Mexican watermelon grower/farmer out of business.

Eventually, the immigration from Mexico will rise substantially, especially from from watermelon farmers.

Yes, that makes perfect sense!