Thinking About Tariffs

I am a bit confused over this tariffs thing so let me see if i have this straight.
If i sell something to America for £100 but they put 10% or 20% tariffs on it so it now costs the American consumers £110-£120, the consumers either pay more or stop buying my thing and start buying something cheaper.
To avoid the tariffs i could move my business to America and sell the things again for £100 there but then if i wanted to sell my things to the rest of the World, because of the retaliatory tariffs put on America by everyone else, the consumers there would have to pay £110 - £180.
So the choices then are to move my business to America and sell to Americans but struggle to sell to the rest of the World or stay where i am and sell to the rest of the World but struggle to sell to America.
Why would anyone do that and restrict their goods to one country and limit their options with the other 194 countries in the World?
It's not a great business plan but it must make sense to Donald Trump, a man who literally managed to bankrupt multiple casinos but maybe he is an economic genius after all and is the guy to reshape the American economy. On the other hand he may tank it completely so let’s find out!
Either way, only 45 months of his presidency left to go.