I say they have a coward mentality because of years of watching the way how England's teams approach competitive sports and how that relates to what i know of the society.
The beauty of international football is that it is reflective of the culture of the nation. Brazil, Germany, Spain, England, China, South Korea... even Trinidad & Tobago exhibit traits that are unique to their culture in the way they play the game (for better or for worse).
I have NEVER seen and England team go for a team's jugular. If England is leading 1-0 in a quarterfinal or semi-final game, i can guarantee for all the years i am watching football that their tactic will be to close up shop and try to avoid losing at all costs, regardless of how on top of the game they are. This is regardless of the opposition or the personnel, they just do not have that.
A great example is the 2002 world cup game against Brazil when they were leading 1-0 up until the 70th minute was it? And as far as i remember, Brazil was down to 10 men yet England fold up into a shell and let Ronaldinho and Rivaldo bore them when they had a great chance to press home their advantage.
I've also seen it in cricket... England is not a team that can go out to dominate the opposition, they are not a team to get in their opponents faces and press and advantage. They play within so much limitations and take very few chances, the only player that operates outside this mould is Keven Pietersen and he is South African.
Tim Henman, well don't get me started on him.
When i tie this to culture, i'm saying that my observation of the English psyche and society from my time living there is that they are non-confrontational and operate alot within limitations.. They doh really step out the box and they doh really express themselves, alot of emphasis is placed on observing norms, stuff like customs and etiquette is a big thing.
You will not see an England team abandon their conservative approach and go all out to attack and opponent from the get go. You will hardly ever see an English player in an important game just smile, relax and enjoy himself a la Ronaldinho, you will never see him try something audacious or against the norm a la Pirlo.. Gascoigne and George Best were the only ones for me who had that but outside of that it is about playing to instructions and to system.
FS, i apologize if you are offended by me calling that a coward mentality, that may have been a bit over the top, but their predictably and refusal to ever try something creative or inventive is what i was alluding to.