As this weekend's Euro referendum in Sweden is clearly demonstrating, there are a number of people in Europe who want to be part of the EU, but not of the Euro.
In order for the Euro to become the "reserve" currency, the Sterling will need to be included. Your argument conveniently sets this point to one side.
Also, for the Euro to emerge all powerful, you need to overcome lingering fiscal, demographic and language (especially, language), geo-political and nationalistic considerations (especially, the last, and without doubt, the first) in order to compete effectively against the single, integrated, US$.
Three other points for consideration:
1) US POPULATION GROWTH
The US is growing and on even the mid-outlook population projections, will approximate 500M by 2050 (the most pessimistic of these projections still put the US at 420M by 2050).
Europe, in contrast, is growing very slowly and, in some instances, its population is actually falling. In the coming years, this will increasingly become factored into the equation as the US$ continues in its role as the reserve currency.
2) EURO HAS EXPORTED EUROPE'S FISCAL DRAG
The impact of the common currency in Europe has been to export the mainstream contagion (being Germany's France's and Italy's economic malaise) throughout Europe and to drag down European growth to negative figures (in the 2nd quarter).
Until Europe reforms its labour laws, and those laws relating to social welfare and security, taxation, and pension reform, the UK will stay away from the Euro, and with this, goes any chance of the Euro being a reserve currency.
3) NEO-COLONIALIST IMPLICATIONS
One of the reasons why the Euro has, in some instances, extended its reach to nearby countries has had everything to do with Europe insisting that, in order to trade, you must trade in Euros.
This has had the effect of politicising the Euro (perhaps, previously, this was also a fault of the US$), but in a more zenophobic, independent world, many nations are increasingly wary of the neo-colonialist cliches that this tosses off.
Maybe the US$ can be similarly accused of this (but that's due to the benefits of incumbency, longevity, and the conduct of global commerce). However, whereas the US has been passive in this way for the last 50 -60 years, the Europeans are being quite intrusive and demanding of their position, etc. If this were not so, then why are a number of EU members not also EURO members?
