Maybe this rise is linked to Pope Benedict's visit in April but again I would have thought most vocations directors would have wanted more contact with a young man than a few months, though they do things faster in USA than here. I think that the cause is American bishops take vocations seriously, they actually ask men if they have considered being a priesthood.

I have shown many American vocations videos and posters, they seem to encourage devotions and piety. I put up one beautiful New York diocesan video showing a Blessed Sacrament procession, with seminarians in clerical dress, and more recently of a boy about eight playing at Mass. I have even had some correspondence with young men in American Colleges considering. American bishops are teaching bishops, the newer generation are teaching from the Catechism. I can't help also thinking that in the US there is a greater variety of diocese, if you find your own "intolerably liberal", as one of my correspondents did, well there are always other bishops or diocese, prospective seminarians are willing to move.
Reading between the lines, I wonder whether one of the causes is the unpopularity of the Iraq war/invasion, it has tended to suggest that young men are capable of making life and death choices about their future, and that the priesthood is manly. The Theology of the Body, teaching on abortion and openness to life have a direct impact on the young, they are young people's issues.
I suspect too that many American Bishops take the morale of their clergy seriously, priests who are convinced of the supreme value of their sacramental ministry, tend to value and seek out vocations. In the UK too many priests tend to think they are going to be the last priest in their parish!