All those Scandinavic languages have their own pecularities. Danish pronunciation is special, but all of them share very much grammar and vocabulary. Swedish is the largest and has generally good resources. Norwegian has a strong Duolingo course, while Danish has an active contributor on Tatoeba and thereby lots of correct sentences on sites drawing from it.
But basically you have no wrong choices: pick any, and you can shift to any other with little effort. Also, the elder generation in each country understands the other languages, while the youngsters might have a bit of an initial threshold to cross.
My background: I studied (but did not learn) Swedish at school, moved to Denmark for one year and have now lived several years in Norway. Jumping from Danish to Norwegian was easy.
However, United Stateses seems to be attractive
– Emma Lincoln Oct 06 '22 at 18:53