Right, and I remember very well these times. It was the time when I paid 30 DEM fees for a remittance to a bank 120 miles away from me, but in a different country. Today, if I do the same, I pay zero to the bank. I´ve come to the conclusion that the benefits overweight the disadvantages, such as one interest rate given by the ECB. Or tell me, why has the US one currency, and not 50?
"Or tell me, why has the US one currency, and not 50?"
Because the U.S. has essentially always been a single national economic entity. There is a very real problem trying to bring such a large basket of economies under one umbrella, especially the umbrella of a common currency. There are benefits, and there are drawbacks, and unfortunately the process of encountering and possibly overcoming the drawbacks is going to be much longer and more drawn out than the process of encountering the benefits. The benefits will be apparent well before the drawbacks have run their course, and that will maintain a degree of unpopularity for the currency among the nations using it.
This is a problem additionally (or especially) compounded by the differences in each of the economies in terms of population, development and specialization, and domestic fiscal policies and situations.
These are not problems anyone denies exists. They're very real, they're very understood and accepted among economists, including those in the employ of Brussels. The question is how well can those drawbacks be managed, and without true political and economic union there is a very real fear among many economists that ultimately the common currency's drawbacks _cannot_ effectively be managed even if it is maintained.
The fact that the Eurozone is wealthy and has a large population will alone give the currency weight and attractiveness, and on those strengths alone the euro should attain a degree of status as a reserve currency. Becoming a match for the dollar as a reserve currency is a very long way away, and the prospect of replacing it as "the" reserve currency is highly unlikely. If the dollar loses its status as "the" reserve currency, there will not be another that takes its place, we will simply revert to a time of "greatest among equals" at the currency table.
Because the 50 states are not, in and of themselves, sovereign nations. The countries that use the Euro are.
And I do sincerely hope you are not falling into the Europhile trap of believing the Eurozone or EU is equivalent to the 50 states of the United States. I cannot count the number of times I've seen this grave misunderstanding propagated, apparently on the idea that, well, the individuals states have their own governments and policies and are then under the umbrella of a federal government.
Because the US is one country. The EU is a communist/marxist non-democratically ruled bloc and not a nation.