Depends on how we define country and continent. Marineford is a small island. Dressrosa a larger one. Mihawk's casual slash is small island level. All out Mihawk might be able to circle around Dressrosa's walls and cut them while staying in the middle, Which is magnitudes above what Zoro did with ISDS, as Pica is tiny compared to Dressrosa and Zoro had to have physical contact.
Even Whitebeard couldn't sink Marineford while raging, even though the Gura is designed for that purpose. Primebeard could rather easily, especially with awakening. I guess all out Primebeard would sink Dressrosa with one attack, causing heavy sea quakes and Tsunami's in the process. But no one in One Piece would destroy like a larger country like Alabasta which has several days travel time. Primebeard might be the only candidate capable of when going on rampage (not even a single attack).
But those feats are still higher than what Bleach displayed in the Arrancar arc. Aizen after leveling up twice, boasted about his new strength as he could destroy a hill with one swing of his sword:
And even then it turned out it wasn't Aizen's swing that destroyed the hill but it was Ichigo. While Mihawk casually slices an island sized ice berg.
Doesn't mean Mihawk >> Aizen though. Aizen even without Hogyoku is stronger than Mihawk, since Aizen has other qualities. While lacking DC, he still has immense lethality, speed, Kido and absolute hypnosis (even that being his Shikai only). Even among Shinigami, he is incredibly strong.
