In the healthcare context, factors which have influenced implementation of strategic plans in the organization include  "receptive contexts" (Pettigrew, Ferlie, & McKee, 1992). Factors such as the environmental pressure, quality and coherence of policy, key people leading change, simplicity and clarity of goals, supportive organizational culture, inter-organizational networks as well as the local context have influenced the success of implementation efforts. 

Among other critical strategic factors (CSF), I would share the Stakeholders Interest approach. Firstly is to identify the county's stakeholders such as the Public, Businesses, Sponsors, Existing and Potential Investors, Federal Government, NGOs and the Board of Governance. Therefore, the strategic decisions and objectives should focusing to satisfying the stakeholders' requirements.

There are a number of factors:

Resources

Implementation agents

Local county policy 

Stakeholder influence 

Perceived benefits

In the US, primarily Politics, which includes city and county officials being influenced through financial structures, such as foreign investments and political contributions, coupled with influential individual financiers and portfolio investment entities, as well as local "anchor" Corporations, and in some cases, citizen ballot measures. Additional factors are localized-targeted-geographic growth areas which are viewed by "KEY INFLUENCERS or County Fathers" as a means to attract new revenue streams and stimulate economic growth which would increase taxable entities resulting in additional tax revenues.

I'd add that a key success implementation factor is the degree of "Openness" the strategic plan really has. Openness involves a three-fold approach: (1) openness before plan formulation, by attracting the right people to participate in the plan, (2) openness during formulation, namely, by collaborating with key actors on the ground as well as local development agents and knowledge actors, and (3) openness at implementation, by sharing results, verificating and validating a key action plan. Bear in mind that without the right degree of "openness" a strategic plan is just a piece of paper, therefore, council management will need that key implementers on the ground agree on the need and method to come to action.

You might be interested the attached article.

Several...read my book...International business the challenges of Globalization. chapter 10 is about Strategy, however, to get a full answer you better read the whole book. 

I would add another factor, namely, the capacity, both economic and political, of the organization that is charged with the responsibility for implementing the strategic plan. See Googin, Lester, Bowman, and O'Toole, Implementation Theory and Practice (1990) for more detail about factors affecting implementation performance.

@John Kagumu knowing the context you are referring to very well, I do concur with Shetty that the Key people leading the change could be the main hindrance or catalyst of strategy implementation. So when it come to the county government, the Governor, the MCAs and Cabinet Secretaries are key. Looking at the few counties that have been able to achieve their strategic plans it was mainly because the leader supported it and took leadership of the same.