In general, I would says that patriotism and nationalism have more-or-less the same meaning,

Not hardly.

but patriotism has good implications

See A. Bierce, above, also:

"Patriotism, though it is based upon the natural and indeed instinctive love of home, has been elevated in the modern world into an unparalleled congeries of imbecilities. What it demands of the individual citizen, as a practical matter, is that he yield not only his judgement but also his property and even his life to whatever gang of scheming politicians happen to be in power. The essence of his virtue as a patriot is that he ask no questions, once the band is set to playing. - H.L. Mencken

and nationalism has bad ones.

See also "jingoism" and "nativism".