Nonlinear Maxwell equations are written up to the third-power deviations from a constantfield background, valid within any local nonlinear electrodynamics including QED with a Euler-Heisenberg (EH) effective Lagrangian. The linear electric response to an imposed static finite-sized charge is found in the vacuum filled by an arbitrary combination of constant and homogeneous electric and magnetic fields. The modified Coulomb field and corrections to the total charge and to the charge density are given in terms of derivatives of the effective Lagrangian with respect to the field invariants. These are specialized for the EH Lagrangian.The large values of electromagnetic fields, close to or larger than m 2 e = 4.4 · 10 13 G = 1.6 · 10 16 V /cm, are present not only in astrophysical objects, such as pulsars, magnetars and quark stars, but also in the close vicinities of elementary particles as produced by their charges, magnetic and electric dipole moments. (For instance, the magnetic field of the neutron at the edge of its electromagnetic radius makes up the value of about 10 16 G, characteristic of magnetars.) This fact is encouraging interest in nonlinear electrodynamics that accounts for the effects of interaction between electromagnetic fields when at least one of them is large. These are, for instance, linear, quadratic and cubic responses of the vacuum, that include large "background" or "external" electromagnetic fields, to probe fields of, say, the ones produced by charges and currents. Another example of nonlinear effects is the correction to the magnetic and electric dipole moments of elementary particles and resonances owing to their self-coupling.Another circumstance that has been fueling interest in the effects of quantum electrodynamics, this time within the framework of (2+1)-dimensional space-time, is the problem of Coulomb impurities in graphene; see the most recent review in Ref [1] and also the recent paper [2]. The point is that the effective coupling in that theory is much larger, and, correspondingly, the values of the fields optimal for nonlinearity are much smaller than in the (3+1)-dimensional QED. Among the possible background fields most handy are those that admit an exact solution to the Dirac equation for the electron, which enables explicitly exploiting the Furry picture in order to take the background exactly while calculating the response functions -the polarization operators of different ranks. These are the plane-wave field (see the review [3]), the Coulomb field (dealt with in Ref.[4]), and the constant homogeneous field [5,6]. However, only the latter admits, strictly speaking, a treatment with the use of a local electromagnetic action. The local approach, thanks to its relative simplicity, proved to be very fruitful in revealing special nonlinear effects [7]. These include the consequences of nonlinearity of quantum electrodynamics stemming from the quantum phenomenon of virtual electron-positron pairs creation by a photon, the pairs interacting with an electromagnetic field befor...