TV has component technology of course, from the ability to transmit wireless signals, to the ability to capture electronic signals from light through a lens, but the main inventor of Television is a Scotsman named John Logie Baird. The Telephone was generally attributed to Alexander Graham Bell (another Scotsman by birth, though he died in Canada), but is disputed. However a whole stream of other inventors are known for integral parts of the technology and techniques. Radio is of course generally credited to Marconi, an Italian in England, but is again, disputed in parts.
America didn't tend to be a leader, or indeed a superpower, until after WWII. That's a factor that came about through America's decision to sit back in the early years of WWII and simply sell weapons, ammo and supplies to other nations. Although once the USA did commit to the war they committed wholeheartedly, they'd already been a destination for years of immigrants who could afford the trip - many of whom were of course the wealthier types, business owners, doctors, scientists, academics, etc. It also meant that while most of the world post-war was impoverished and struggling to rebuild their cities and infrastructure, America had a huge amount of war debts pouring a stream of extra cash into their country, which aside from that one attack on Pearl Harbour, had almost no damage to infrastructure at all.
Throughout the next few decades after the war, the USA actively used it's strong financial advantage to recruit even more top scientists from all over the world. In Europe and the UK this was referred to as 'The Brain Drain', and referred to the fact that promising students, successful scientists, or owners of interesting patents would be offered far higher wages and funding by US institutions than the European counterparts could match. It was a huge investment, but has paid off in spades in the past 5 decades, although they still make lousy cars.