Many states in the US are as large as countries in Western Europe. Both Texas and Alaska are larger than France in land size.
If the US broke apart, California and Texas would take 2 slots in the top 10 world economies (by GDP) with NY at 11 and Florida behind them beating out Spain. Less known states (in terms of world recognition) beat out many countries too. Illinois beating Switzerland & Pennsylvania running about even. Ohio, Georgia, Washington (the state, not dc) N. Carolina soundly outpacing Belgium, Sweden & Ireland. etc
For size, population and GDP, the combined countries of west Europe (that is fuzzily grouped together for these purposes) is comparable to the collection of states in the US. Thus, should either be compared by similar US State to single European country, or USA to the Western Europe conglomerate of countries.
That is how many Americans see the US. Culture, customs and even beliefs and language* can vary between states in ways one would think they are in a different country. This way of American's seeing the US vs Europe also relates to geography, sure, most Americans can't point European countries on a map and name them, but how many people outside NA can locate & name US states that are not CA, NY, or maybe TX?
* yeah it's pretty much all english, but there are a few distinctly different version of english where some could have trouble understanding each other (as can happen in large countries). Some 13% speaks Spanish. While it's all Spanish, Texas Spanish is not the same as California Spanish; try using your very limited Texas Spanish in Spain if you want funny looks.